1. Field of the Invention
The present invention relates to a side release buckle comprising a socket member having openings on sides thereof and a plug member having arm portions which are releasably inserted into the socket member and engageable with the openings. More specifically, the present invention relates to a side release buckle having increased engaging strength and having no risk of a fault operation in inserting the plug member into the socket member.
2. Description of the Related Art
Buckles of various structures have been well known, each of which is comprised of a female member composed of a socket member and a male member composed of a plug member, molded of synthetic resin. Speaking of its basic structure, the socket member has engaging faces, while the plug member comprises arm portions which are adapted to be releasably inserted into the socket member and engaging portions on the arm portion which engage and disengage from the engaging faces of the socket member. Each of the socket member and plug member has a base portion at its one side end thereof. A belt insertion hole is formed in each of the base portions. An end of the belt is inserted through the belt insertion hole and fixed thereto. By engaging/disengaging the socket member and/from plug member, both the belt ends can be connected to or disconnected from each other.
Among these buckles, there is a type in which openings are formed side walls of the socket member, and by fitting the engaging portions formed at front ends of the arm portions of the plug member into the openings, engaging faces of the engaging portions engage the respective parts of the openings, so that the plug member is connected to the socket member. To release this connection, side faces of the engaging portions which engage the openings so as to be exposed outside are nipped with fingers and pushed in so as to deform the arm portions resiliently. Then, the engaging portions are removed from the openings, thus the plug member is pulled out of the socket member.
A general type buckle of this kind has two arm portions extending in parallel from a base portion of the plug member, and shoulder portions are formed at front ends of arm portions so as to be projected outward from side faces of the arm portions. The arm portions are inserted into a cavity of the socket member while being resiliently deformed. When the shoulder portions reach the side face openings of the socket member, the resilient deformation of the arm portions is returned to their original state, and at the same time, the shoulder portions are inserted into the openings so that they engage portions of the opening rear end faces. Because sections of the shoulder portions cannot be formed larger than a section of the cavity, the engagement between the socket member and plug member is achieved by only engagement between the opening rear end faces formed by the right and left side walls and the shoulder portions.
Therefore, when an external force is applied to exposed surfaces of the shoulder portions while the socket member and the plug member are connected to each other, the shoulder portions are resiliently deformed so that they move easily into the cavity of the socket member. Therefore the plug member is easy to slip out of the socket member. Further, when a strong pulling force is applied to both the socket member and plug member in their connection direction, the shoulder portions and portions of the opening end faces of the side walls are damaged, so that the engaging force drops. Thus, sometimes, a sufficient function of the buckle cannot be exerted.
According to U.S. Pat. No. 5,737,810 (Japanese Patent Laid-Open Publication No. 10-117814) or U.S. Pat. No. 5,794,316, (Japanese Patent Laid-Open Publication No. 10-57114), areas of the engaging faces between the openings of the socket member and the shoulder portions of the plug member are increased so as to increase an engaging force therebetween. Particularly in the latter buckle, such an engaging structure has been proposed that distribution of the areas of the engaging faces is made uniform so as to ensure a desired strength in the engaging portions.
An engaging/disengaging structure of the buckle disclosed in the aforementioned U.S. Pat. No. 5,794,316, will be briefly described. In each of the engaging portions of the plug member, a notch portion is formed between the arm portion and the engaging portion by cutting it out. Thickness of an extended portion of the arm portion is designed to be larger than that of a projecting portion so that a step is formed between the projecting portion and the arm portion. The extended portion in the longitudinal direction of the arm portion and the portion projecting outward are constructed integrally in such a manner that a hooking face composed of lateral V-shaped or lateral U-shaped section which engages the engaging face of the socket member is formed by the step and an outer edge of the projecting portion. Each side wall portion of the cavity of the socket member is substantially the same as a contour of each lateral section of the projecting portion of the plug member. A gap between an upper wall and a bottom wall of the side wall portion is substantially the same as thickness of the extended portion of the engaging portion of the plug member.
According to the aforementioned structure of the buckle disclosed in the aforementioned U.S. Pat. No. 5,794,316, the engaging strength against a pulling increases and the strength of the engaging portion itself is improved as mentioned in the publication. However, a moving distance for the hooking face to slip out of the engaging face of the socket member is almost uniform in an entire portion of the hooking face. Further, when an unexpected external force is applied to the engaging portion of the plug member exposed outside, the projecting portion of the engaging portion is shifted horizontally into the cavity. Therefore, a process in which the engagement is released is determined only by the aforementioned moving distance irrespective of the sectional shape of the hooking face. This moving distance is necessarily limited by a structure of the buckle.
That is, even in the buckle described in the above publication, when the engaging face of the plug member slips out of the engaging face of the socket member, all the engaging faces are entirely unlatched at the same time. As a result, it never happens that even when part of the engaging face is released, the engagement of the other part is not maintained. Therefore, when an unexpected outside force is applied to the engaging portion of the plug member as described above, at the same time when the engaging portion is shifted in the aforementioned limited moving distance, the engagement is released all at once. Thus, it never happens that even when the engaging portion is shifted in such a moving distance, the engagement is still maintained. Therefore, the aforementioned buckle is not different from the conventional buckle in that the plug member easily slips out of the socket member.
Accordingly, the present invention has been achieved to solve the above problems and carry out a further improvement. An object of the invention is to provided a side release buckle in which an engaging strength between the socket member and plug member is secured, strength of engaging portions of the both members is improved, even when an unexpected external force is applied to the engaging portion of the plug member, the engaging portions are more unlikely to be released than the conventional ones and when the plug member is inserted into the socket member, the front and rear sides are not mistaken.
The above object is achieved effectively by the first to seventh aspects of the invention described below.
According to a first aspect of the invention, there is provided a side release buckle comprising a socket member and a plug member, said socket member including a top wall, a bottom wall, a pair of right and left side walls for connecting said top wall and said bottom wall with a gap therebetween and openings communicating with a cavity inside the socket member and disposed inside from said side walls, said plug member including at least one arm portion projecting from a base portion thereof and an engaging portion which engages part of said socket member at a front end of the arm portion. The arm portion of said plug member is adapted to be resiliently deformed when it is inserted into/released from said cavity of said socket member so that a hooking face of the engaging portion of said arm portion releasably engages an end face of said opening. The engaging portion is subject to a composite movement comprised of a movement perpendicular to an insertion/release direction of said arm portion and directed inward and outward of said opening and a movement toward either said top wall or bottom wall. The composite movement is generated by a composite movement generating means. Part of an end face of said opening which releasably engages hooking faces of the engaging portion of said plug member is an opening end face of the bottom wall or top wall which is opposite to a movement of said engaging portion toward the top wall or bottom wall respectively, and an opening end face of said side wall.
In the conventional buckle of this kind as well as the buckle disclosed in the above-mentioned publication, when arm portions of a plug member is inserted into a cavity of a socket member to engage the plug member from the socket member, or when an engaging portion of the plug member engaging an opening of the socket member is pressed with fingers so as to release the engagement with the socket member, a movement of the engaging portion formed at an end portion of the arm portion of the plug member caused by resilient deformation of the arm portion is all in a direction between inside and outside of the opening which is perpendicular to an extending direction of the arm portion. Thus, an engaging face composed of an end face of the opening of the socket member, which engages a hooking face of the engaging portion of the plug member, is only a side wall portion of the opening end face even when a shape of the engaging portion is modified in any way.
On the other hand, according to the present invention, the engaging movement of the engaging portion of the plug member with respect to the socket member is a composite movement comprised of a movement perpendicular to an extension of the arm portion of the plug member and in the direction between inward and outward of the opening of the socket member, and a movement directed to a top wall or bottom wall of the socket member. Therefore, the engaging face of the opening of the socket member which engages the hooking face of the engaging portion of the plug member can be both the opening end face of a bottom wall or top wall located on an opposite side to a direction of movement of the aforementioned engaging portion toward the top wall or bottom wall of the socket member, and the opening end face of the side wall.
As a result, an engaging area between the engaging portion of the plug member and engaging face of the socket member is increased largely, and an engaging strength at the time of pulling is intensified. Further, the strengths of the engaging portion of the plug member and the engaging faces of the socket member themselves can be improved. Further, at the time of engagement, the hooking face of the engaging portion of the plug member engages two opening end faces of the socket member which join in a vertical direction and substantially horizontal direction. Therefore, if an unexpected external force is applied to the engaging portion exposed out of the opening and the engagement of the opening end face is partially released, the engagement through the other opening end face is maintained temporarily. Therefore, possibility that the engagement is released by the aforementioned external force is reduced as compared to the conventional buckle.
Furthermore, since the engaging face of the opening and the hooking face of the engaging portion are engaged with each other at two faces of the upper wall side and the side wall sides, almost no steps are formed between an outer face of the top wall of the socket member and an outer face of inclined wall portions of the plug member, and between an outer face of a side wall of the socket member and an outer face of a vertical wall portion of the engaging portion of the plug member. Therefore, the buckle looks generally flat, giving a good appearance.
Further, the openings of the socket member are defined by largely cutting out the socket member toward a center of the top wall thereof. As a result, the engaging portion of the plug member to engage with each of the openings is exposed outside of the top wall of the socket member to a large extent, so that it is easy to hold the engage portion by fingers, facilitating engagement and disengagement of the buckle.
When the engaging portion of the plug member is disengaged from the opening of the socket member, the engaging portion is pushed obliquely downward. Therefore, although the engaging area between the engaging portion and the opening is large, an amount of shifts of the engaging portion, i.e. amount of deformation of the arm portion becomes much smaller so that the disengagement can be easily achieved.
The hooking face of the engaging portion may be in an arrowhead shape while the engaging face of the opening that faces the hooking face is shaped in a slope. In this case, the engaging force between the socket and plug members is increased so that the buckle can not be accidentally separated.
According to a second aspect of the invention, the composite movement generating means includes the arm portion having a twisting structure around a projecting direction thereof. Thus, when an external force is applied in one direction to the engaging portion at an end of the arm portion, components of force, for example, in a horizontal direction and vertical direction are generated by the twisting structure of the arm portion, so that the arm portion is deformed resiliently in a direction to restore the twisting while being rotated about an axis line of the arm portion. As a result, when an external force is applied in one direction to the arm portion or the external force applied is released, the engaging portion is rotated along said twisting of the arm portion and moves obliquely which is a result of composition of a movement in the horizontal direction and a movement in the vertical direction, so that the engaging portion is moved in the cavity of the socket member in the inward and outward direction.
According to a third aspect of the invention, the composite movement generating means includes the arm portion having a sectional shape to be resiliently deformed in a direction of the composite movement. That is, by forming the sectional shape of the arm portion in such a shape that the arm portion is easily deformed in a direction of a predetermined angle between the horizontal direction and vertical direction, even when an external force is applied in the horizontal direction, a component of force acts in a direction in which the arm portion is easily deformed. As a result, the arm portion is resiliently deformed in a direction of the aforementioned inclination angle.
According to a fourth aspect of the invention, at least one of the top wall and bottom wall of the socket member is symmetrical with respect to a center line along a longitudinal direction of the socket member and comprised of inclined walls which are inclined so that a height of the right and left side walls is smaller than a height of a center portion of the socket member including the center line. Thus, the cavity at a center in the width direction of the socket member is larger vertically than that at the right and left end portions. Therefore, it allows a sufficient resilient deformation of the arm portion of the plug member to the cavity. The top wall and bottom wall of the socket member may be formed symmetrically with respect to a horizontal plane.
According to a fifth aspect of the invention, one of the top wall and bottom wall of the socket member is symmetrical with respect to a center line of the socket member and comprised of inclined walls which are inclined so that a height of the right and left side walls is smaller than a height of a center portion of the socket member including the center line, and the top wall or bottom wall opposing to the inclined walls is comprised of a horizontal wall perpendicular to the side walls. Thus, because either the top wall or bottom wall of the socket member is an inclined face, the top surface or bottom surface of the socket member are not mistaken, so that no insertion error of the arm portion of the plug member occurs. Thus, the plug member can be inserted into the socket member securely. Of course, the top wall and bottom wall can be designed to be parallel to each other.
According to a seventh aspect of the invention, a thickness of the opening end face of either one of the top wall and bottom wall which the hooking faces of the engaging portion of the plug member releasably engage is larger than a thickness of the opening end face of the other one of the bottom and top walls opposing said one of the top and bottom walls. With this structure, an engaging area between the engaging portion of the plug member and the engaging face of the socket member can be increased, and further, the engaging strength and the strength against pulling can be increased. Furthermore, a wall of the socket member which is not to be engaged with the engaging portion of the plug member can be designed to be thin as much as possible if a minimum necessary strength of the socket member can be secured. This leads to reduction of material cost.